This invention is related generally to wireless communications systems. More particularly, it is related to antennas for use with indoor wireless communications and voice networks.
Current indoor wireless solutions fasten antenna radomes to ceilings, walls, columns and the like. These solutions are aesthetically undesirable. There is a need for an indoor wireless antenna installation that is not visible. There is a need for a wireless solution that addresses both the wireless local area network (WLAN) and in-building voice network applications.
Commercial wireless communications systems use the radio frequency spectrum from 800 MHz to approximately 5 Ghz. Most such systems include a fixed, wired infrastructure and portable devices. The portable devices reach the infrastructure via access points or base stations. Current architecture of wireless systems such as a cellular telephone system includes a fixed portion of geographically-separated base stations and a number of remote communications devices. A base station has at least one transceiver that communicates with remote terminals by exchanging RF signals employing various formats and access techniques, such as frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), etc. Communication channels are implemented by frequency modulating RF carrier signals near frequencies of 800 MHZ, 900 MHz, 1800 MHz and/or 1900 MHz. General aspects of cellular telephone systems are known in the art.
A wireless local area network is a flexible data communications system implemented as an extension or alternative to wired local area networks. Wireless LANs transmit and receive data over the air using radio frequency (RF) technology, minimizing the need for wired connections. Wireless LANs combine user mobility with data connectivity. The data being transmitted is superimposed on the RF carrier wave by frequency modulation. Multiple RF carrier waves can exist in the same space at the same time without interference if the RF carrier waves are transmitted on different frequencies.
In a typical wireless LAN configuration, a transmitter/receiver device, called an access point, connects to the wired network from a fixed location using standard cabling. A single access point can support a small group of users and can operate within a range up to several hundred feet. The access point or antenna attached to the access point is normally mounted high to obtain the desired transmission and reception coverage.
One type of WLAN network architecture is the xe2x80x9cinfrastructurexe2x80x9d (IEEE 802.11b protocol standard). An 802.11b WLAN operates in the 2.4 Ghz band. This architecture uses fixed network access points with which mobile client devices can communicate. Access points hand off mobile client devices from one access point to another in a manner that is invisible to the mobile client device, providing unbroken connectivity. Wireless devices are equipped with a special network interface card (NIC) as well as an antenna, transceiver and circuitry to convert the analog RF signals into digital signals used by computers.
The distance over which RF waves can communicate is a function of transmitted power and receiver design, and the propagation path in indoor environments. Most wireless LANs use RF since RF waves can penetrate most indoor walls and obstacles. The range of coverage for wireless LANs can vary from less than a hundred to greater than 300 feet.
The present invention provides a method for constructing a patch style antenna in which the dielectric substrate is the ceiling tile (also referred to as ceiling panel) itself, and the radiating element and the ground plane are fixed to the face and back of the panel, respectively. Since the ceiling panel acts as the antenna, the back of the ceiling panel does not have to be routed out to create a cavity for the antenna pod, as is done currently. The sizes of the radiating element and the ground plane are not an issue; no miniaturization of the elements is required. The present invention provides a wider bandwidth and higher gain due to the thicker dielectric substrate used for the ceiling panel construction. Therefore, it is easier to achieve multiple resonances (i.e., multiple frequencies). The present invention also provides more freedom to design around various additional components.
A patch style antenna comprises four elements: the ground and radiating planes, the dielectric substrate separating the two, and connecting means such as a coaxial cable. The new element added by the present invention is the replacement of the typical thin plastic or epoxy material associated with microstrip antennas by a relatively thick substrate that already performs the primary function of serving as an acoustical ceiling panel. The acoustical ceiling panel has the dual function of providing an acoustical barrier and serving as a communications antenna at the same time. The acoustical ceiling panel becomes an active part of the antenna, rather than acting as a host for an embedded antenna.
The unique aspect of the invention is that the acoustical ceiling panel material itself serves as the dielectric substrate. This simplifies the manufacture and increases the design flexibility of antennas. Since the acoustical ceiling panel is the antenna, there is no need to attach discrete antennas to the acoustical ceiling panel as in the current method.